[applets/mediacontroller] Don't use Album Art for icon
Summary:
Icon of Media Player applet is missing in the System Tray settings when
the media playing has a cover. Such icon is present when nothing is playing.
Fix by not using album art in any case - icon is not longer used in
tooltip, can be static.
BUG: 420197
FIXED-IN: 5.19.0
Test plan:
- play audio/video with a player compatible with Media Player applet
- open system tray settings during playback
- Icon of Media Player applet is always present in system tray
settings, regardless of state.